Equatorial spread-F (ESF) is the phenomenon of plasma instability in the Earth's ionosphere that scatters radio waves that pass though it, inducing signal loss. Small scale fluctuations (scintillations) in ESF form a phase screen, which acts as a diffraction grating, producing Fraunhofer diffraction. The velocity of these scintillations can be estimated using two or more GPS receivers aligned in the zonal (geomagnetic East) direction, and measuring the time lag between signal peaks as the diffraction pattern moves along the receiver plane. Subsequently, geometric effects can be factored into the velocity estimation to reference the components to the Earth's magnetic fields and account for receiver misalignments along these axes.
Two GPS L1 receivers located in CTIO, Chile, were used to measure 50-Hz GPS SNR data, and subsamples of data with observed scintillation were cross-correlated with one another. Results from the data confirm that the scintillations travel in the Eastward zonal direction with mean velocities ranging from about 50 to 130 m/s, which shows some agreement with the results from other experimental setups that attempt to estimate zonal scintillation velocity.